Systems and methods for determining, broadcasting and using reference atmospheric data in a network of transmitters

ABSTRACT

Determining, broadcasting and using reference pressure data in a network of transmitters. Particular embodiments described herein include machines that select atmospheric data from weather stations within a transmitter network, use the selected atmospheric data to determine a reference atmospheric value, and transmit the reference atmospheric value from a transmitter to a mobile device for use in estimating an altitude of the mobile device. The atmospheric data may include any of reference pressures form the weather stations, measured temperatures from the weather stations, or reference temperatures from the weather stations. The reference atmospheric value may include a reference pressure value of a reference altitude, or a reference temperature value.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/930,315, filed on May 12, 2020, which claims priority to U.S.Provisional Patent Application No. 62/874,811, filed on Jul. 16, 2019,all of which is hereby incorporated by reference in its entirety and forall purposes.

BACKGROUND

Determining the exact location of a mobile device (e.g., a smart phoneoperated by a user) in an environment can be quite challenging,especially when the mobile device is located in an urban environment oris located within a building. Imprecise estimates of the mobile device'saltitude, for example, may have life or death consequences for the userof the mobile device since the imprecise altitude estimate can delayemergency personnel response times as they search for the user onmultiple floors of a building. In less dire situations, imprecisealtitude estimates can lead a user to the wrong area in an environment.

Different approaches exist for estimating an altitude of a mobiledevice. In a barometric-based positioning system, altitude can becomputed using a measurement of pressure from a calibrated pressuresensor of a mobile device along with ambient pressure measurement(s)from a network of calibrated weather stations and a measurement ofambient temperature from the network or other source. An estimate of analtitude of a mobile device (h_(mobile)) can be computed by the mobiledevice, a server, or another machine that receives needed information asfollows:

$\begin{matrix}{{h_{mobile} = {h_{sensor} - {\frac{{RT}_{remote}}{gM}{\ln\left( \frac{P_{sensor}}{P_{mobile}} \right)}}}},} & \left( {{Equation}1} \right)\end{matrix}$

where P_(mobile) is the estimate of pressure at the location of themobile device by a pressure sensor of the mobile device, P_(sensor) isan estimate of pressure at the location of a weather station that isaccurate to within a tolerated amount of pressure from true pressure(e.g., less than 5 Pa), T_(remote) is an estimate of temperature (e.g.,in Kelvin) at the location of the weather station or a differentlocation of a remote temperature sensor, h_(sensor) is an estimatedaltitude of the weather station that is estimated to within a desiredamount of altitude error (e.g., less than 1.0 meters), g corresponds tothe acceleration due to gravity (e.g., −9.8 m/s²), R is a gas constant,and M is molar mass of air (e.g., dry air or other). The minus sign (−)may be substituted with a plus sign (+) in alternative embodiments ofEquation 1, as would be understood by one of ordinary skill in the art(e.g., g=9.8 m/s²). The estimate of pressure at the location of theweather station can be converted to an estimated reference-levelpressure that corresponds to the weather station in that it specifies anestimate of pressure at the latitude and longitude of the weatherstation, but at a reference-level altitude that likely differs from thealtitude of the weather station. The reference-level pressure can bedetermined as follows:

$\begin{matrix}{{P_{ref} = {P_{sensor} \times {\exp\left( {- \frac{{gM}\left( {h_{ref} - h_{sensor}} \right)}{{RT}_{remote}}} \right)}}},} & \left( {{Equation}2} \right)\end{matrix}$

where P_(sensor) is the estimate of pressure at the location of theweather station, P_(ref) is the reference-level pressure estimate, andh_(ref) is the reference-level altitude. The altitude of the mobiledevice h_(mobile) can be computed using Equation 1, where h_(ref) issubstituted for h_(sensor) and P_(ref) is substituted for P_(sensor).The reference-level altitude h_(ref) may be any altitude and is oftenset at mean sea-level (MSL). When two or more reference-level pressureestimates are available, the reference-level pressure estimates arecombined into a single reference-level pressure estimate value (e.g.,using an average, weighted average, or other suitable combination of thereference pressures), and the single reference-level pressure estimatevalue is used for the reference-level pressure estimate P_(ref).

Reference pressures from one or more weather stations can be combinedinto a reference pressure value that a cellular transmitter transmits(e.g., broadcasts) to mobile devices for use in computing theirestimated altitudes or for other uses (e.g., calibrating pressuresensors of the mobile devices). By way of example, FIG. 1 illustrates acellular network that includes a set of transmitters 110 configured totransmit signals 113 using known transmission technologies. The signals113 can be transmitted at different times for acquisition by a mobiledevice 120 as the mobile device 120 moves through the cellular network.The mobile device 120 may take different forms, including a mobile phoneor other wireless communication device, a portable computer, anavigation device, a tracking device, a receiver, or another suitabledevice that can receive the signals 113. A network backend 130 with acontrol unit—e.g., a positioning server such as eSMLC/LMF(Evolved-Serving Mobile Location Center/Location Management Function)—isconnected to the transmitters 110. The backend 130 includes processors(e.g., servers) for performing different types of processing—e.g.,collecting reference pressures from weather stations, generatingreference pressure values based on collected reference pressures, andother types of processing. Examples of possible components in thetransmitters 110, the mobile device 120, and the backend 130 are shownin FIG. 12 and discussed in the ‘Other Aspects’ section near the end ofthis disclosure.

The signals 113 transmitted from the transmitters 110 contain differenttypes of information. One type of information is often referred to as“assistance data”. Assistance data can be used by the mobile device 120(or backend 130) to compute an estimated position of the mobile device120 in terms of latitude, longitude and/or altitude. As previouslydescribed, one approach for computing an estimated altitude usesassistance data that includes reference pressures that are based onmeasurements of pressure from one or more weather stations, and in somecases uses reference temperatures that are based on measurements oftemperature from one or more weather stations. As shown in FIG. 1 ,different weather stations 115 are positioned at different locationsthroughout the cellular network. Each of the weather stations 115 candetermine a reference pressure for a reference altitude (e.g., sea-levelaltitude), and may measure temperatures. Reference pressure values to betransmitted by the transmitters 110 can be determined based on referencepressures from the weather stations 115. Similarly, a referencetemperature can be transmitted by the transmitters 110, where thatreference temperature can be determined based on temperatures measuredby the weather stations 115. Ideally, each transmitter transmits areference pressure value that was generated using recently-generated andhighly-accurate reference pressures from weather stations that are nearthat transmitter. In some embodiments, each transmitter transmits areference temperature value that was generated using recently-measuredand highly-accurate temperatures measured by weather stations that arenear that transmitter (e.g., using an average of measured temperatures).Ideal circumstances cannot be expected for all cellular networks.Instead, factors that affect the reliability of available referencepressures and/or temperatures must be addressed, including (i) theproximity of a transmitter to weather stations that provide referencepressures and/or temperatures, (ii) the age of reference pressuresand/or temperatures—e.g., the time since measurements of pressure usedto determine the reference pressures were made or since the temperatureswere measured, and (iii) the quality of the reference pressures and/ortemperatures—e.g., how recently the weather station was calibrated, theresolution of data from the weather station, exposure of the weatherstation to over-heating, or some other known conditions that may affectthe reliability of the reference pressure and/or temperature. Therelative locations of transmitters and weather stations will often varyin a network of transmitters. For example: a transmitter and a weatherstation can be co-located (e.g., weather station 115 a is located withinthe footprint of transmitter 110 a); two or more weather stations can benear a transmitter (e.g., weather stations 115 b and 115c are within athreshold distance of transmitter 110 b); or no weather station is neara transmitter (e.g., transmitter 110 c). The age and quality ofreference pressures and/or temperatures can also vary among weatherstations. Given the potential differences in relative locations, ages,and/or qualities associated with reference pressures and/or temperaturesfrom weather stations in different cellular networks, different methodsfor collecting reference pressures and/or temperatures from weatherstations are needed to optimize use of available reference pressures forcomputing a reference pressure value and/or use of available temperaturemeasurements for computing a reference temperature value under differentcircumstances impacting different transmitters.

Even after reference pressure values and/or reference temperature valuesare computed, those values must be transmitted to mobile devices (e.g.,UEs) using limited and highly valuable bandwidth. In some wirelessnetworks, the reference values are transmitted to mobile devices viapoint-to-point protocols, such as LPP (LTE Positioning Protocol) [TS36.355] or SUPL (Secure User Plane Location) Protocol [OMA SUPL] overthe wireless network. However, in use cases where there is a highconcentration of mobile devices, such as a high-rise building orstadium, it is more efficient to broadcast the reference values viapoint-to-multi-point. In order to support accurate computations ofaltitude at any time, transmitter networks must allocate valuablebandwidth for broadcasting updated reference pressure values and/orreference temperatures on a regular basis. However, regular broadcastsof reference pressure values and/or reference temperatures mayunnecessarily occupy bandwidth during periods of time when changes inpressure and/or temperature within the cellular network are so limitedthat older reference pressure values still reflect actual pressureconditions and/or older temperature measurements still reflect actualtemperature conditions in the cellular network. On the other hand,regular broadcasts of reference pressure values may not keep up withchanges in pressure within the cellular system such that referencepressure values stored on a mobile device become stale before updatedreference pressure values are received. Thus, methods for adaptivelymodifying when to broadcast reference values can decrease consumption ofvaluable network resources and also improve accuracy of estimatedaltitudes over time, which is highly desirable. Alternatively, methodsfor adaptively modifying when mobile devices search the broadcastchannel for reference values when previous reference values are stalecan increase power savings, which is highly desirable.

Although adjustments to a broadcast schedule offer advantages in somesituations, those adjustments may not provide sufficiently-accuratereference pressure values in other situations, such as when weatherstations do not produce new reference pressures at a rate that is equalto or greater than the desired adjusted rate of broadcasts, or when amobile device enters an area in which no broadcasts of referencepressure values are available. Hence, methods for using informationabout weather changes that are expected within a transmitter network toadjust reference pressure values offers advantages during situationswhen adjustments to broadcast scheduling would not necessarily providesufficiently accurate reference pressure values.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an operational environment in which systems and methodsfor determining, broadcasting and using reference pressure data in anetwork of transmitters may operate.

FIG. 2A through FIG. 2F illustrate different cellular elements for usein determining reference pressure data in a network of transmitters.

FIG. 3 depicts a process for determining reference pressure data that istransmitted to mobile devices.

FIG. 4 depicts a process for selecting one or more reference pressuresfrom one or more weather stations within a transmitter network.

FIG. 5 depicts a process for determining a reference pressure value of areference altitude to be transmitted.

FIG. 6 depicts a process for determining if a reference pressure valueis valid.

FIG. 7A depicts a process for generating a new reference pressure valueby adjusting a reference pressure value.

FIG. 7B depicts a process for generating a new reference pressure valueby adjusting reference pressures used to compute a previous referencepressure value.

FIG. 8 depicts a process for determining reference pressure data that isused to compute altitude estimates of mobile devices or calibratepressure sensors of mobile devices.

FIG. 9A and FIG. 9B depict processes for determining if a receivedreference pressure value is valid.

FIG. 10A through FIG. 10D depict processes for determining arepresentative reference pressure value by combining reference pressurevalues.

FIG. 11A through FIG. 11C depict processes for determining a newreference pressure value.

FIG. 12 illustrates components of a transmitter, a mobile device, and anetwork backend.

DETAILED DESCRIPTION

One approach for estimating of an altitude of a mobile device usingreference pressures from weather stations is described in the Backgroundsection of this disclosure. Typically, weather stations that aredispersed throughout a cellular network provide reference pressures foruse in determining a reference pressure value that is transmitted from acellular transmitter to a receiver that is within range of thattransmitter. The reliability of the resultant reference pressure valueis impacted by different aspects of a cellular network, includingproximity of weather station to transmitter, age of reference pressure,and quality of reference pressure value, as well as changes in weatherconditions over time.

Unfortunately, many cellular networks do not include sufficient numbersof weather stations and/or sufficient distribution of weather stationsin the vicinity of each transmitter in those networks. Given the variednumbers and distributions of weather stations around differenttransmitters in a cellular network, different approaches are needed forevaluating candidate reference pressures that can be used to generate areference pressure value to be transmitted by a transmitter. Asdiscussed further below, different types of cellular elements within acellular network can be used to select reference pressures from weatherstations based on relationships between the weather stations and thecellular element. Examples of cellular elements, which are illustratedin FIG. 2A through FIG. 2F, include a transmitter, a coverage area ofthe transmitter, a sub-cell occupied by the transmitter (e.g., micro,pico or other sub-cell), a cell sector used by the transmitter, acoverage area of a transmission beam, an area along a direction of asignal transmitted by the transmitter, or sets of the foregoing cellularelements.

-   (i) For deployments that include multiple weather stations within    each cellular element (e.g., large cellular elements like coverage    areas of different transmitters), a control unit in the network such    as a positioning server (e.g., eSMLC/LMF) can compute a reference    pressure value for a transmitter based on a mathematical combination    of selected reference pressures from weather stations within a    cellular element associated with that transmitter. Different    mathematical combinations of selected reference pressures are    possible, including weighted averages where weights are based on    proximity of weather stations to the cellular element (or a portion    of the cellular element), age of the reference pressures, qualities    of the reference pressures, and/or other characteristics of the    reference pressures or weather stations. In some implementations, a    control unit may acquire or construct an isobar plot for an area    that includes the cellular element, and use the plot to determine a    reference pressure value that is best-suited for the mobile device    (e.g., that is located at an estimated position of the mobile    device).-   (ii) For deployments where there is a many-to-one mapping between    cellular elements and weather stations (or where a particular    cellular element associated with a transmitter does not include any    weather station), a control unit may select reference pressures    based on proximity of weather stations to a cellular element even if    the weather stations are not in a threshold vicinity of the cellular    element, and/or may select reference pressures based on the age of    reference pressures, based on quality of the reference pressures,    and/or based on some other condition.-   (iii) For deployments where there is one-to-one mapping between    cellular elements and weather stations, a control unit may use a    reference pressure from the weather station within a cellular    element as the reference pressure value to be transmitted by the    transmitter associated with that cellular element.-   (iv) For deployments with a mix of (i), (ii) and (iii) above, a    control unit may use different ways of selecting reference pressures    depending on the number of weather stations in each cellular element    associated with each transmitter, such that different approaches for    selecting reference pressures can be used for different    transmitters—e.g., using (i) for a first transmitter, using (ii) for    a second transmitter, and (iii) for a third transmitter.    Alternatively, different types of cellular elements can be used to    select a threshold amount of reference pressures for each    transmitter—e.g., using a small cellular element (e.g., cell sector)    for a first transmitter when that small cellular element includes    weather stations that provide at least the threshold amount of    reference pressures, and using a large cellular element (e.g., cell)    for a second transmitter because a small cellular element for the    second transmitter does not include weather stations that provide at    least the threshold amount of reference pressures, but the large    cellular element includes weather stations that provide at least the    threshold amount of reference pressures.    In any deployment, different types of cellular elements can be used    to select reference pressures for different transmitters depending    on circumstances impacting each transmitter.

Changes in weather conditions over time can also affect the reliabilityof reference pressure values. Different cellular networks are deployedin different regions that experience different types of pressure changesover time. These changes in pressure affect the validity of referencepressure values. As discussed further below, a control unit of acellular network can monitor weather within the cellular network—e.g.,by accessing weather reports that detail actual and expected changes inpressure over time and distance in different areas of the network—and todetermine expected changes in pressure within cellular elements.Expected changes in pressure can be used to determine expiration timesfor reference pressure values associated with particular cellularelements, which can be used to increase or decrease the rate at whichnew reference pressure values are determined and transmitted to mobiledevices from transmitters associated with those cellular elements.Modifications to the rate at which new reference pressure values aredetermined and transmitted to mobile devices allow for more-efficientbandwidth usage while ensuring more accurate reference pressure values(and more-accurate altitude estimates) over time compared to systemsthat do not adjust broadcast schedules in the same way.

Alternatively, changes in pressure over time can be determined and usedto adjust previously computed reference pressure values without any needfor computing a new reference pressure value using new referencepressures, which reduces the time needed to compute reliable referencepressure values, and provides reliable reference pressure values duringtimes when a new reference pressure value based on new referencepressures cannot be determined or received. Changes in pressure acrossdistances can be monitored and used to limit the validity of referencepressure values to particular areas within the cellular network, suchthat a moving mobile device can determine if previously receivedreference pressure values can be used for the mobile device's currentlocation. When a mobile device has moved since last receiving areference pressure value, changes in pressure across the distancetraveled by the mobile device can be determined and used to adjust thatreference pressure value without any need for obtaining a new referencepressure value, which reduces bandwidth use, reduces times needed tocompute reliable reference pressure values, and provides reliablereference pressure values during times when a new reference pressurevalue based on new reference pressures cannot be determined or received.Changes across distance may be represented in different ways, includingcomputed gradients.

Different embodiments that incorporate the above aspects are discussedbelow.

Determining Reference Pressure Data That is Transmitted to MobileDevices

FIG. 3 depicts a process for determining reference pressure data that istransmitted to mobile devices.

Initially, reference pressures from weather stations within atransmitter network are selected for use in determining a referencepressure value of a reference altitude to be transmitted by atransmitter (step 310). One embodiment of step 310 is depicted in FIG. 4, which is described later.

The selected reference pressures are used to determine a referencepressure value to be transmitted by a transmitter (step 320). Oneembodiment of step 320 is depicted in FIG. 5 , which is described later.

The transmitter transmits the determined reference pressure value (step330), which is received by any mobile device that is inside a coveragearea of the transmitter. By way of example, the transmitter may be acellular transmitter that transmits scheduled broadcast signals atregular intervals. Alternatively, in other implementations, thetransmitter transmits the reference pressure value to a particularmobile device after receiving a request for the reference pressure valuefrom that mobile device.

At a time after initially transmitting the previous reference pressurevalue, a determination is made if transmission of a new referencepressure value is scheduled for that time (step 340). If transmission ofa new reference pressure value is not scheduled for that time, step 340is repeated.

In one embodiment (option 1), if transmission of a new referencepressure value is scheduled for that time, the process returns to step310. In another embodiment (option 2), if transmission of a newreference pressure value is scheduled for that time, a determination ismade as to whether a previously-determined (e.g., most-recentlydetermined) reference pressure value is valid (step 350). One embodimentof step 350 is depicted in FIG. 6 , which is described later.

If the reference pressure value is still valid, the process returns tostep 330, and the reference pressure value is transmitted to the mobiledevice.

If the reference pressure value is not valid, a new reference pressurevalue is generated (step 360).

In a first embodiment of step 360, the new reference pressure value isgenerated by selecting newer reference pressures from weather stationsand determining the new reference pressure value using the same processas used for step 320, but with the newer reference pressures instead ofthe older reference pressures from step 310. Optionally, any schedulefor determining and transmitting reference pressure values over time canbe adjusted based on monitored pressure conditions. For example, (i) arate of pressure change in the network or in an area that includes thetransmitter and/or weather stations that provided selected referencepressures can be determined (e.g., from regional or more defined weatherreports), and (ii) the rate of pressure change can be used to determinea maximum time between reference pressure value determinations andtransmissions by dividing a maximum amount of tolerated change inpressure (e.g., 10 Pa) by the rate of pressure change, and using theresulting time as the maximum time between reference pressure valuedeterminations and transmissions.

In a second embodiment of step 360, the new reference pressure value isgenerated by adjusting the older reference pressure value from step 320based on measured or expected changes in pressure since the time whenthe reference pressure value was determined during step 320. Exampleimplementations of the second embodiment of step 360 are depicted inFIG. 7A and FIG. 7B, which are described later.

Lastly, the transmitter transmits the new reference pressure value (step370)—e.g., to any mobile device that resides within a coverage area ofthe transmitters, or to a particular mobile device for embodiments thatpermit requests for new reference pressure values from such a mobiledevice.

In an alternative embodiment (not shown), steps 310 through 340 areperformed, except that a determination during step 340 that transmissionof a new reference pressure value is not scheduled for that time resultsin determining if the reference pressure value is valid (step 350),after which the process (i) returns to step 340 if the referencepressure value is valid, and (ii) advances to 360 if the referencepressure value is not valid. After step 360, the process returns to step340.

In an alternative embodiment (not shown), step 340 is omitted, and step350 is performed after step 330.

By way of example, the network backend 130 and/or a processor of thetransmitter can be used to perform steps 310, 320, 340, 350 and 360.

Selecting One or More Reference Pressures From One or More WeatherStations Within a Transmitter Network (Step 310)

FIG. 4 depicts a process for selecting one or more reference pressuresfrom one or more weather stations within a transmitter network for usein determining a reference pressure value during an embodiment of step310.

A cellular element associated with the transmitter is optionallydetermined (step 411). By way of example, different cellular elementsare illustrated in FIG. 2A through FIG. 2F, including the transmitteritself, a coverage area of the transmitter, a sub-cell occupied by thetransmitter, a cell sector used by the transmitter, a coverage area of atransmission beam, an area along a direction of a signal transmitted bythe transmitter, or other cellular elements. Sets of these cellularelements could also be used as a “cellular element” that is determinedin some embodiments. Any process known in the art for defining theboundaries and characteristics of each cellular element can be used.

Reference pressures from weather stations that meet one or moreconditions are selected (step 412).

In a first embodiment of step 412, n reference pressures from nrespective weather stations that meet a proximity-based condition areselected. In one implementation, reference pressures from each weatherstation within the cellular element, within a threshold distance (forexample: 100 yards; 1 mile; or 10 miles) from part of the cellularelement (e.g., a coordinate of the cellular element), or within an areathat includes the cellular element can be selected. In anotherimplementation, reference pressures from the nearest n weather stationsto part of the cellular element are selected.

In a second embodiment of step 412, n reference pressures from nrespective weather stations that meet an age-based condition areselected (for example: reference pressure measure is less than 10minutes old, or less than 1 hour old). In one implementation, eachreference pressure with an age that is below a threshold age value isselected. In another implementation, the n most-recent referencepressures are selected. In yet another implementation, each referencepressure that is valid—e.g., has not expired—is selected.

In a third embodiment of step 412, n reference pressures from nrespective weather stations that meet a quality-based condition areselected. In one implementation, each reference pressure with a qualitythat is above a threshold quality value is selected. In anotherimplementation, the n reference pressures with the highest quality areselected. A quality metric can be determined for each referencepressure, where higher values of the metric represent higher quality. Byway of example, if the metric is based on time since a weather stationwas calibrated, a higher metric value would be given for more recentcalibration. By way of another example, if the metric represents if aweather station experiences over-heating (e.g., from sun exposure orHVAC exhaust), a high metric value is given to reference pressures thatoriginate from weather stations that do not experience over-heatingwhile a low metric value is given to reference pressures that originatefrom weather stations that experience over-heating. By way of example, aquality metric may be a tolerance in the pressure measurement where alower tolerance indicates a higher quality.

In a fourth embodiment of step 412, n reference pressures from nrespective weather stations that meet two or more conditions selectedfrom proximity-based, age-based, or quality-based conditions areselected. Different orders of conditions are possible—e.g., apply aproximity-based condition to identify a set of candidate referencepressures, and then apply an age-based or quality-based condition toidentify the selected reference pressures, or vice versa.

In a fifth embodiment, a series of conditions are tested until referencepressures are selected or until there are no more conditions to test. Inone implementation, a first condition is tested (e.g., proximity), andif no reference pressures are selected based on the first condition thena second condition is tested (e.g., age), and so on for otherconditions. In another implementation, a set of conditions are tested(e.g., proximity and age), and if no reference pressures are selectedbased on the set of conditions then a portion of the set of theconditions is tested (e.g., proximity only), and if no referencepressures are selected based on that portion of the set of conditionsthen another portion of the set of the conditions is tested (e.g., ageonly), and so on for other portions of the set of conditions.

Optionally, if no reference pressures from weather stations meet the oneor more conditions, a new cellular element may be determined (step 413a), and the process returns to step 412 for the new cellular element.

In one embodiment of the process depicted in FIG. 4 , the new cellularelement is another type of cellular element associated with thetransmitter—e.g., the first type of cellular element is a cellularelement associated with a smaller area such as a transmission beamdirected from a transmitter towards the mobile device or a cell sector,and the second type of cellular element is a type of cellular elementassociated with a larger area such as a coverage area of thetransmitter. Initially using a cellular element associated with asmaller area to select reference pressures increases the accuracy of areference pressure value relative to a mobile device since the smallercellular element is more likely to select reference pressures that areexperiencing similar pressure conditions as the mobile device.

In another embodiment of the process depicted in FIG. 4 , the newcellular element is the same type of cellular element, but is associatedwith a different transmitter (e.g., a different transmitter adjacent tothe transmitter). The new cellular element is a neighboring (e.g.,adjacent) cellular element of the same type that is associated with thesame transmitter or a different transmitter—e.g., if the first cellularelement is a cell sector of a cell in which a transmitter resides, thenthe new cellular element may be an adjacent cell sector in that samecell; e.g., if the first cellular element is a cell in which atransmitter resides, then the new cellular element may be an adjacentcell in which a neighboring transmitter resides.

Optionally, if no reference pressures from weather stations meet the oneor more conditions, a message indicating that no reference pressurevalue is available can be generated and transmitted (step 413 b).

Different embodiments of FIG. 4 include different sets of the steps. Afirst embodiment includes steps 411, 412 and 413. A second embodimentonly includes step 412 (i.e., there is consideration of conditions, butthere is no consideration of cellular elements).

The processes of FIG. 3 and FIG. 4 can be performed for differenttransmitters, and the results may be different for differenttransmitters depending on the distribution of weather stations relativeto the different transmitters—e.g., no performance of step 413 a may berequired to produce selected reference pressures for a firsttransmitter, but performance of step 413 a may be required to produceselected reference pressures for a second transmitter.

Determining a Reference Pressure Value at a Reference Altitude to beTransmitted (Step 320)

FIG. 5 depicts a process for determining a reference pressure value at areference altitude to be transmitted during an embodiment of step 320,which comprises computing the reference pressure value using an averageof the selected reference pressures (step 521).

In one implementation of step 521, the average is a weighted averagethat uses weights based on an inverse of respective distances betweenweather stations of the selected reference pressures and part of thecellular element (e.g., a coordinate or other feature of the cellularelement), such that a reference pressure from a weather station that iscloser to the cellular element is given greater weight than a referencepressure from another weather station that is further away from thecellular element. Since reference pressure can change over distance,closer reference pressures more-accurately reflect reference pressure atthe two-dimensional location of the transmitter than reference pressuresthat are further away.

In another implementation of step 521, the average is a weighted averagethat uses weights based on an inverse of respective ages of the selectedreference pressures, such that a reference pressure that ismore-recently determined is given greater weight than a referencepressure that was determined further in the past. Since pressure canchange over time, recently-determined reference pressuresmore-accurately reflect reference pressure at the current time thanolder reference pressures.

In yet another implementation of step 521, the average is a weightedaverage that uses weights based on respective qualities of the selectedreference pressures, such that a reference pressure that originates froma more-reliable source is given greater weight than a reference pressurethat originates from a less-reliable source. Since weather stations canexperience different issues (e.g., rate of drift, over-heating, etc.),reference pressures from more-reliable weather stations (e.g., weatherstations that have been recently calibrated, that have less or nooverheating, etc.) to more-accurately reflect actual reference pressurethan reference pressures from less-reliable weather stations (e.g.,weather stations that have not been recently calibrated, that areaffected by overheating, etc.).

In yet another implementation of step 521, the average is a weightedaverage that uses weights based on two or more of respective distances,respective ages, or respective qualities.

Determining if a Reference Pressure Value is Valid (Step 350)

FIG. 6 depicts a process for determining if a reference pressure valueis valid during an embodiment of step 350.

Initially, a time at which pressure in the network is expected to changeby a threshold amount of pressure since a past instance of time isdetermined (step 651). In different embodiments, the past instance oftime can be when the reference pressure value was determined, when aselected reference pressure was determined, or another time. In oneembodiment, the time is determined by dividing the threshold amount ofpressure by an expected rate of pressure change to yield an amount oftime, and then adding the amount of time to the past instance of time todetermine the time at which pressure in the network is expected tochange by the threshold amount of pressure. The threshold amount ofpressure can vary in different embodiments. In one embodiment, thethreshold amount of pressure is set to an amount of pressurecorresponding to a maximum amount of tolerated error for estimatedaltitudes (e.g., 10 Pa). In some embodiments, the determination duringstep 651 is of a time at which pressure is expected to change by thethreshold amount of pressure within a particular area of the networkthat includes the transmitter and/or a weather station that provided areference pressure used to compute the reference pressure value.Restricting step 651 to pressure changes within particular areas makesthe determination more relevant to pressure conditions that are actuallyexpected to affect the transmitter and/or weather stations. In someembodiments, the area may be determined by cellular element as discussedabove.

An expiration time for the reference pressure value, before which thereference pressure value is valid and after which the reference pressurevalue is invalid, is determined based on the determined time (step 652).In one embodiment of step 652, the expiration time is the determinedtime. In another embodiment of step 652, the expiration time is a timethat precedes the determined time by a threshold amount of time (e.g., tunits of time).

An area in which the reference pressure value is valid can be determinedwith or without an expiration time. The area may be a particularlocalized pressure zone among other localized pressure zones, such thatthe reference pressure value is only valid in the particular localizedpressure zone. Alternatively, the area may be an area in the networkthat is not expecting changes in pressure that are expected for otherareas in the network, such that the reference pressure value is notvalid in those other areas.

Generating a New Reference Pressure Value (Step 360)

FIG. 7A and FIG. 7B depict processes for generating a new referencepressure value during different embodiments of step 360.

FIG. 7A depicts a process for generating a new reference pressure valueby adjusting a reference pressure value, which comprises adjusting thereference pressure value by an amount of pressure change that occurredsince the reference pressure value was determined (step 761 a). Theamount of pressure change that occurred can be determined in differentways, for example, including measurements of the pressure change fromweather stations in the network or from a weather report.

FIG. 7B depicts a process for generating a new reference pressure valueby adjusting reference pressures that were used to compute the previousreference pressure value. For each reference pressure of the selectedreference pressures that originated from an area in which pressurechanged in excess of a threshold amount of pressure since the referencepressure was determined, that reference pressure is adjusted by anamount of pressure change that occurred since that reference pressurewas determined (step 761 b), and the new reference pressure value iscomputed using an average of the adjusted reference pressures (step 762b). In one implementation of step 762 b, the average is a weightedaverage that uses weights based on an inverse of respective distancesbetween weather stations of the adjusted reference pressures and part ofthe cellular element. In another implementation of step 762 b, theaverage is a weighted average that uses weights based on an inverse ofrespective ages of the reference pressures that were adjusted. In yetanother implementation of step 762 b, the average is a weighted averagethat uses weights based on respective qualities of the referencepressures that were adjusted. Alternatively, the average may be aweighted average that uses weights based on two or more of respectivedistances, respective ages, or respective qualities

As indicated above with respect to step 330 of FIG. 3 , a mobile devicethat is within a coverage area of the transmitter can receive areference pressure value transmitted by the transmitter. That mobiledevice can use the received reference pressure value to determinereference pressure data for use in estimating an altitude of the mobiledevice or for other uses (e.g., calibrating a pressure sensor of themobile device). As discussed below with respect to FIG. 8 , differentapproaches can be used to determine such reference pressure data.

Determining Reference Pressure Data That is Used to Compute AltitudeEstimates of Mobile Devices or Calibrate Pressure Sensors of MobileDevices

FIG. 8 depicts a process for determining reference pressure data thatcan be used to compute altitude estimates of mobile devices.Alternatively, the reference pressure data can be used to calibratepressure sensors of mobile devices, or other uses that are known in theart.

Initially, a mobile device receives a reference pressure value for areference altitude that was transmitted by a transmitter (step 810).

At any time after receiving the reference pressure value, and beforereceiving any new reference pressure value from the transmitter, adetermination is made as to whether the reference pressure value isvalid (step 820). Embodiments of step 820 are depicted in FIG. 9A andFIG. 9B, which are described later.

If the reference pressure value is determined to be valid during step820, a first representative reference pressure value is determined bycombining the reference pressure value received from the transmitterwith any other valid reference pressure values received from othertransmitters (step 830). Embodiments of step 830 are depicted in FIG.10A, FIG. 10B, FIG. 10C, and FIG. 10D, which are described later.

After the first representative reference pressure value is determined,it can be used with the reference altitude and a pressure value measuredby a pressure sensor of the mobile device to estimate an altitude of themobile device (step 840).

If the reference pressure value is determined to be not valid duringstep 820, a new reference pressure value is determined by adjusting thereference pressure value received from the transmitter based on changesin pressure in the network that have occurred since the referencepressure value was originally determined or since the reference pressurevalue was received (step 850). Embodiments of step 850 are depicted inFIG. 11A, FIG. 11B, and FIG. 11C, which are described later.

After the new reference pressure value is determined, a secondrepresentative reference pressure value is determined by combining thenew reference pressure value with one or more other new referencepressure values and or valid older reference pressure valuescorresponding to other transmitters (step 860)—e.g., using the sameprocess as used for step 830.

After the second representative reference pressure value is determined,it can be used with the reference altitude and the pressure valuemeasured by the pressure sensor of the mobile device to estimate thealtitude of the mobile device (step 870—e.g., using the same process asused for step 840.

By way of example, a processor of the mobile device can be used toperform steps 820, 830, 840, 850, 860 and 870. Alternatively,information needed to perform some or all of these steps can be providedfrom the mobile device to the network backend 130 of FIG. 1 using knowncommunication pathways, and the backend 130 performs those steps.

Determining if a Received Reference Pressure Value is Valid (Step 820)

FIG. 9A and FIG. 9B depict processes for determining if a receivedreference pressure value is valid during embodiments of step 820.

During FIG. 9A, an expiration time of the reference pressure value isreceived by the mobile device from a transmitter (step 921 a), and adetermination is made if the reference pressure value is valid (step 922a). In one implementation, the reference pressure is valid when the timeat which step 922 a is performed is before the expiration time, and thereference pressure value is not valid if the time at which step 922 a isperformed is after the expiration time.

During FIG. 9B, a time at which pressure in the network is expected tochange by a threshold amount of pressure since a past instance of timeis determined (step 921 b). In different embodiments, the past instanceof time can be when the reference pressure value was determined, when aselected reference pressure was determined, or another time. In oneembodiment, the time is determined by dividing the threshold amount ofpressure by an expected rate of pressure change to yield an amount oftime, and then adding the amount of time to the past instance of time todetermine the time at which pressure in the network is expected tochange by the threshold amount of pressure. The threshold amount ofpressure can vary in different embodiments. In one embodiment, thresholdamount of pressure is set to an amount of pressure corresponding to amaximum amount of tolerated error for estimated altitudes (e.g., 10 Pa).In some embodiments, the determination during step 921 b is of a time atwhich pressure is expected to change by the threshold amount of pressurewithin a particular area of the network that includes the transmitterand/or a weather station that provided a reference pressure used tocompute the reference pressure value. Restricting step 921 b to pressurechanges within particular areas makes the determination more relevant topressure conditions that are actually expected to affect the transmitterand/or weather stations.

An expiration time for the reference pressure value, before which thereference pressure value is valid and after which the reference pressurevalue is invalid, is determined based on the determined time (step 922b). In one embodiment of step 922 b, the expiration time is thedetermined time. In another embodiment of step 652, the expiration timeis a time that precedes the determined time by a threshold amount oftime.

A determination is made if the reference pressure value is valid (step923 b). In one implementation, the reference pressure is valid when thetime at which step 923 b is performed is before the expiration time, andthe reference pressure value is not valid if the time at which step 923b is performed is after the expiration time.

In some embodiments, an area of validity for a reference pressure valuecan also or alternatively be determined and then provided to a mobiledevice. In these embodiments, an estimated position of the mobile devicecan be computed (e.g., latitude and longitude). A determination is madeif the estimated position is within the area of validity, or within athreshold distance of the area of validity. If so, the referencepressure value is treated as valid. If not, the reference pressure valueis treated as not valid.

Using Validity of Reference Pressure Value to Control Whether a MobileDevice Searches a Broadcast Channel

In some embodiments, step 820 of FIG. 8 , including the sub-steps ofFIG. 9A or FIG. 9B can be performed to determine the validity of areference pressure value that was previously received from atransmitter. If the value is valid, a decision is made at the mobiledevice to not have the mobile device search for a broadcast of a newreference pressure value. Not searching can continue until thepreviously received reference pressure value is no longer valid, afterwhich the mobile device searches for a new reference pressure value.Alternatively, the search for a new reference pressure value may startat a predetermined amount of time prior to the end of validity undercircumstances when the end of validity is known. Advantages of using thevalidity of a reference pressure value to control whether a mobiledevice searches a broadcast channel for a new reference pressure valueinclude power savings and increases in processing capacity whilesearching is not being performed.

Determining a Representative Reference Pressure Value by CombiningReference Pressure Values (Step 830)

FIG. 10A through FIG. 10D depict processes for determining arepresentative reference pressure value by combining reference pressurevalues during embodiments of step 830.

During FIG. 10A, the n most-recently determined reference pressurevalues are selected from m received reference pressure values, wherein mis greater than n (step 1031 a), and the representative referencepressure value is computed by combining the n selected referencepressures (step 1032 a). In one implementation, the combination is aweighted average based on an inverse of the ages.

During FIG. 10B, the n reference pressure values having the longestvalidity times are selected from m received reference pressure values,wherein m is greater than n (step 1031 b), and the representativereference pressure value is computed by combining the n selectedreference pressures (step 1032 b). In one implementation, thecombination is a weighted average based on an inverse of the validitytimes.

During FIG. 10C, the n reference pressure values from n respectivetransmitters that are closest to an estimated location of the mobiledevice are selected from m received reference pressure values, wherein mis greater than n (step 1031 c), and the representative referencepressure value is computed by combining the n selected referencepressures (step 1032 c). In one implementation, the combination is aweighted average based on an inverse of distances between the ntransmitters and the estimated position of the mobile device.

During FIG. 10D, the representative reference pressure value is computedusing a weighted average of the received reference pressure values (step1031 d). In different implementations, the weights can be based on anyof inverses of ages, inverses of lengths of validity times, and/orinverses of distances (e.g., between the n transmitters and theestimated position of the mobile device).

Determining a New Reference Pressure Value (Step 850)

FIG. 11A through FIG. 11C depict processes for determining a newreference pressure value during embodiments of step 850.

During FIG. 11A, the reference pressure value is adjusted by an amountof pressure change that occurred since the reference pressure value wasdetermined (step 1151 a).

During FIG. 11B, an estimated position of the mobile device isdetermined (step 1151 b), an expected amount of change in pressurebetween the estimated position of the mobile device and a previousestimated position at which the reference pressure value was received isdetermined (step 1152 b), and the reference pressure value is adjustedby the expected amount of change in pressure (step 1153 b).

During FIG. 11C, an estimated position of the mobile device isdetermined (step 1151 c), an expected amount of change in pressurebetween the estimated position of the mobile device and the transmitteris determined (step 1152 c), and the reference pressure value isadjusted by the expected amount of change in pressure (step 1153 c).

Additional Operations for Networks That Use Requests for AssistanceInformation From Mobile Devices

Different systems can benefit from the approaches described above,including (i) systems that broadcast assistance information (e.g.,reference pressure values) on a schedule, and (ii) systems that transmitreference pressure values in response to receiving requests from mobiledevices for a reference pressure value. In the latter systems,additional functionality may be used. For example, mobile devices canmonitor times when particular reference pressure values expire. If areasof validity are used, the mobile devices can also monitor areas in whichparticular reference pressure values are not valid. If a referencepressure value from a transmitter has expired, or is not valid in anarea in which the mobile device is believed to reside (e.g., based oncomparison of an estimated position of the mobile device and an area ofvalidity for the reference pressure value), the mobile device can ignorethat reference pressure value, adjust it, request an adjustment to thereference pressure value (or an adjusted reference pressure value) fromthe transmitter or the network backend, or request a new referencepressure value from the transmitter if still in range of thetransmitter.

Application of Methods to Other Data Provided by Weather Stations

Discussion above has been generally focused on reference pressures andreference pressure values. However, the approaches can be modified aswould be understood by one of ordinary skill in the art to selecttemperature measurements of weather stations before using the selectedtemperature measurements to determine a reference temperature value foruse in the altitude computation that is based on selected temperaturemeasurement(s) from weather station(s). For example, each of the methodscould be modified to replace “pressure” with “temperature”. Forembodiments where reference temperatures are not used, then measuredtemperatures that were measured at different altitudes can replacereference pressures of the reference altitude. Selection of temperatureor reference temperatures could be based on proximity, age, quality, oranother condition. Similarly, the approaches can be modified as would beunderstood by one of ordinary skill in the art to select humidity (orreference humidity), other atmospheric parameters, or any data that isavailable from weather stations. Use of measured temperatures todetermine a reference temperature value can involve averaging themeasured temperatures (e.g., based on weights) to determine thereference temperature value, or adjusting the measured temperatures toreference temperatures at a reference altitude (e.g., using techniquesthat are known in the art) before averaging the resultant referencetemperatures to determine the reference temperature value. Selection ofmeasured temperatures from weather stations can also be limited toweather stations with altitudes that are within a range of acceptablealtitudes (e.g., altitudes within X units of distance from the referencealtitude or another altitude, such as a ground-level altitude in thevicinity of the mobile device).

The term “reference data” refers to any of: reference pressure(s) fromweather station(s); measured temperature(s) or reference temperature(s)from weather station(s); or other atmospheric data from weatherstation(s). The term “reference value” refers to any of: referencepressure value(s) determined from reference pressure(s); referencetemperature value(s) determined from measured temperature(s) orreference temperature(s); or other reference atmospheric data valuesdetermined from atmospheric data collected from weather station(s).

Other Aspects

Discussion above has been generally focused on reference pressures andreference pressure values. However, the approaches can be modified aswould be understood by one of ordinary skill in the art to selecttemperatures for weather stations before using the selected temperaturesto determine a reference temperature value for use in the altitudecomputation that is based on reference temperature(s) from weatherstation(s). Selection could be based on proximity relative to a cellularelement, age, quality or other condition. Similarly, the approaches canbe modified as would be understood by one of ordinary skill in the artto select humidity or other atmospheric parameters, or to select anydata that is available from weather stations.

Different protocols known in the art for transmitting reference pressurevalues, reference temperature values, locations of transmitters, etc.,are contemplated, including use of system information blocks (SIBs).

Any method (also referred to as a “process” or an “approach”) describedor otherwise enabled by disclosure herein may be implemented by hardwarecomponents (e.g., machines), software modules (e.g., stored inmachine-readable media), or a combination thereof. In particular, anymethod described or otherwise enabled by disclosure herein may beimplemented by any concrete and tangible system described herein. By wayof example, machines may include one or more computing device(s),processor(s), controller(s), integrated circuit(s), chip(s), system(s)on a chip, server(s), programmable logic device(s), field programmablegate array(s), electronic device(s), special purpose circuitry, and/orother suitable device(s) described herein or otherwise known in the art.One or more non-transitory machine-readable media embodying programinstructions that, when executed by one or more machines, cause the oneor more machines to perform or implement operations comprising the stepsof any of the methods described herein are contemplated herein. As usedherein, machine-readable media includes all forms of machine-readablemedia, including but not limited to one or more non-volatile or volatilestorage media, removable or non-removable media, integrated circuitmedia, magnetic storage media, optical storage media, or any otherstorage media, including RAM, ROM, and EEPROM, that may be patentedunder the laws of the jurisdiction in which this application is filed,but does not include machine-readable media that cannot be patentedunder the laws of the jurisdiction in which this application is filed.Methods disclosed herein provide sets of rules that are performed.Systems that include one or more machines and one or more non-transitorymachine-readable media for implementing any method described herein arealso contemplated herein. One or more machines that perform orimplement, or are configured, operable or adapted to perform orimplement operations comprising the steps of any methods describedherein are also contemplated herein. Each method described herein thatis not prior art represents a specific set of rules in a process flowthat provides significant advantages in the field of determining,broadcasting and using reference pressure data in a network oftransmitters. Method steps described herein may be order independent andcan be performed in parallel or in an order different from thatdescribed if possible to do so. Different method steps described hereincan be combined to form any number of methods, as would be understood byone of ordinary skill in the art. Any method step or feature disclosedherein may be omitted from a claim for any reason. Certain well-knownstructures and devices are not shown in figures to avoid obscuring theconcepts of the present disclosure. When two things are “coupled to”each other, those two things may be directly connected together, orseparated by one or more intervening things. Where no lines orintervening things connect two particular things, coupling of thosethings is contemplated in at least one embodiment unless otherwisestated. Where an output of one thing and an input of another thing arecoupled to each other, information sent from the output is received inits outputted form or a modified version thereof by the input even ifthe information passes through one or more intermediate things. Anyknown communication pathways and protocols may be used to transmitinformation (e.g., data, commands, signals, bits, symbols, chips, andthe like) disclosed herein unless otherwise stated. The words comprise,comprising, include, including and the like are to be construed in aninclusive sense (i.e., not limited to) as opposed to an exclusive sense(i.e., consisting only of). Words using the singular or plural numberalso include the plural or singular number, respectively, unlessotherwise stated. The word “or” and the word “and” as used in theDetailed Description cover any of the items and all of the items in alist unless otherwise stated. The words some, any and at least one referto one or more. The terms may or can are used herein to indicate anexample, not a requirement—e.g., a thing that may or can perform anoperation, or may or can have a characteristic, need not perform thatoperation or have that characteristic in each embodiment, but that thingperforms that operation or has that characteristic in at least oneembodiment. Unless an alternative approach is described, access to datafrom a source of data may be achieved using known techniques (e.g.,requesting component requests the data from the source via a query orother known approach, the source searches for and locates the data, andthe source collects and transmits the data to the requesting component,or other known techniques).

FIG. 12 illustrates components of a transmitter, a mobile device, and aserver. Examples of communication pathways are shown by arrows betweencomponents.

By way of example in FIG. 12 , each of the transmitters may include: amobile device interface 11 for exchanging information with a mobiledevice (e.g., antenna(s) and RF front end components known in the art orotherwise disclosed herein); one or more processor(s) 12; memory/datasource 13 for providing storage and retrieval of information and/orprogram instructions; atmospheric sensor(s) 14 for measuringenvironmental conditions (e.g., pressure, temperature, humidity other)at or near the transmitter; a server interface 15 for exchanginginformation with a server (e.g., an antenna, a network interface, orother); and any other components known to one of ordinary skill in theart. The memory/data source 13 may include memory storing softwaremodules with executable instructions, and the processor(s) 12 mayperform different actions by executing the instructions from themodules, including: (i) performance of part or all of the methods asdescribed herein or otherwise understood by one of skill in the art asbeing performable at the transmitter; (ii) generation of positioningsignals for transmission using a selected time, frequency, code, and/orphase; (iii) processing of signaling received from the mobile device orother source; or (iv) other processing as required by operationsdescribed in this disclosure. Signals generated and transmitted by atransmitter may carry different information that, once determined by amobile device or a server, may identify the following: the transmitter;the transmitter's position; environmental conditions at or near thetransmitter; and/or other information known in the art. The atmosphericsensor(s) 14 may be integral with the transmitter, or separate from thetransmitter and either co-located with the transmitter or located in thevicinity of the transmitter (e.g., within a threshold amount ofdistance).

By way of example FIG. 12 , the mobile device may include: a transmitterinterface 21 for exchanging information with a transmitter (e.g., anantenna and RF front end components known in the art or otherwisedisclosed herein); one or more processor(s) 22; memory/data source 23for providing storage and retrieval of information and/or programinstructions; atmospheric sensor(s) 24 for measuring environmentalconditions (e.g., pressure, temperature, other) at the mobile device;other sensor(s) 25 for measuring other conditions (e.g., inertialsensors for measuring movement and orientation); a user interface 26(e.g., display, keyboard, microphone, speaker, other) for permitting auser to provide inputs and receive outputs; another interface 27 forexchanging information with the server or other devices external to themobile device (e.g., an antenna, a network interface, or other); and anyother components known to one of ordinary skill in the art. A GNSSinterface and processing unit (not shown) are contemplated, which may beintegrated with other components (e.g., the interface 21 and theprocessors 22) or a standalone antenna, RF front end, and processorsdedicated to receiving and processing GNSS signaling. The memory/datasource 23 may include memory storing software modules with executableinstructions, and the processor(s) 22 may perform different actions byexecuting the instructions from the modules, including: (i) performanceof part or all of the methods as described herein or otherwiseunderstood by one of ordinary skill in the art as being performable atthe mobile device; (ii) estimation of an altitude of the mobile devicebased on measurements of pressure form the mobile device andtransmitter(s), temperature measurement(s) from the transmitter(s) oranother source, and any other information needed for the computation);(iii) processing of received signals to determine position information(e.g., times of arrival or travel time of the signals, pseudorangesbetween the mobile device and transmitters, transmitter atmosphericconditions, transmitter and/or locations or other transmitterinformation); (iv) use of position information to compute an estimatedposition of the mobile device; (v) determination of movement based onmeasurements from inertial sensors of the mobile device; (vi) GNSSsignal processing; or (vii) other processing as required by operationsdescribed in this disclosure.

By way of example FIG. 12 , the server may include: a mobile deviceinterface 31 for exchanging information with a mobile device (e.g., anantenna, a network interface, or other); one or more processor(s) 32;memory/data source 33 for providing storage and retrieval of informationand/or program instructions; a transmitter interface 34 for exchanginginformation with a transmitter (e.g., an antenna, a network interface,or other); and any other components known to one of ordinary skill inthe art. The memory/data source 33 may include memory storing softwaremodules with executable instructions, and the processor(s) 32 mayperform different actions by executing instructions from the modules,including: (i) performance of part or all of the methods as describedherein or otherwise understood by one of ordinary skill in the art asbeing performable at the server; (ii) estimation of an altitude of themobile device; (iii) computation of an estimated position of the mobiledevice; or (iv) other processing as required by operations described inthis disclosure. Steps performed by servers as described herein may alsobe performed on other machines that are remote from a mobile device,including computers of enterprises or any other suitable machine.

Certain aspects disclosed herein relate to estimating the positions ofmobile devices—e.g., where the position is represented in terms of:latitude, longitude, and/or altitude coordinates; x, y, and/or zcoordinates; angular coordinates; or other representations. Varioustechniques to estimate the position of a mobile device can be used,including trilateration, which is the process of using geometry toestimate the position of a mobile device using distances traveled bydifferent “positioning” (or “ranging”) signals that are received by themobile device from different beacons (e.g., terrestrial transmittersand/or satellites). If position information like the transmission timeand reception time of a positioning signal from a beacon are known, thenthe difference between those times multiplied by speed of light wouldprovide an estimate of the distance traveled by that positioning signalfrom that beacon to the mobile device. Different estimated distancescorresponding to different positioning signals from different beaconscan be used along with position information like the locations of thosebeacons to estimate the position of the mobile device. Positioningsystems and methods that estimate a position of a mobile device (interms of latitude, longitude and/or altitude) based on positioningsignals from beacons (e.g., transmitters, and/or satellites) and/oratmospheric measurements are described in co-assigned U.S. Pat. No.8,130,141, issued Mar. 6, 2012, and U.S. Pat. Pub. No. 2012/0182180,published Jul. 19, 2012. It is noted that the term “positioning system”may refer to satellite systems (e.g., Global Navigation SatelliteSystems (GNSS) like GPS, GLONASS, Galileo, and Compass/Beidou),terrestrial transmitter systems, and hybrid satellite/terrestrialsystems.

This application relates to the following related application(s): U.S.Pat. Appl. No. 62/874,811, filed 2019 Jul. 16, entitled SYSTEMS ANDMETHODS FOR DETERMINING, BROADCASTING AND USING REFERENCE ATMOSPHERICDATA IN A NETWORK OF TRANSMITTERS. The content of each of the relatedapplication(s) is hereby incorporated by reference herein in itsentirety.

1. A method comprising: determining a cellular element associated with atransmitter of a transmitter network; selecting reference data from oneor more weather stations, wherein the reference data meets a proximitycondition relative to the cellular element; using the selected referencedata to determine a reference value; and transmitting the referencevalue from a transmitter of the transmitter network to a mobile device.2. The method of claim 1, further comprising: calibrating a barometricpressure sensor of the mobile device using the reference value.
 3. Themethod of claim 1, further comprising: estimating an altitude of themobile device using the reference value.
 4. The method of claim 1,further comprising: after transmitting the reference value, determiningthat a broadcast is scheduled at a first time; and in response to thebroadcast being scheduled at the first time: selecting new referencedata from the one or more weather stations; using the new reference datato determine a new reference value; and transmitting the new referencevalue from the transmitter to the mobile device or another mobiledevice.
 5. The method of claim 1, further comprising: after transmittingthe reference value, determining that a broadcast is scheduled at afirst time; in response to the broadcast being scheduled at the firsttime, determining occurrences of the reference value being valid andbeing not valid; in response to the reference value being valid,transmitting the reference value from the transmitter to the mobiledevice or another mobile device; and in response to the reference valuebeing not valid: generating a new reference value; and transmitting thenew reference value from the transmitter to the mobile device or theother mobile device.
 6. The method of claim 5, wherein the determiningof the occurrences of the reference value being valid and being notvalid comprises: determining a time at which an atmospheric condition inthe transmitter network is expected to change by a threshold amount ofthe atmospheric condition since the reference value was determined,wherein the atmospheric condition is pressure when the reference valueis a reference pressure value, and the atmospheric condition istemperature when the reference value is a reference temperature value;and determining, based on the determined time, an expiration time forthe reference value before which the reference value is valid and afterwhich the reference value is not valid, wherein the expiration time isthe determined time or a time that precedes the determined time by athreshold amount of time.
 7. The method of claim 5, wherein thereference value is a reference pressure value, and wherein generatingthe new reference value comprises: adjusting the reference pressurevalue by an amount of pressure change that occurred in the transmitternetwork since the reference pressure value was determined, wherein thenew reference value is the result of adjusting the reference pressurevalue.
 8. The method of claim 5, wherein the selected reference dataincludes selected reference pressures, wherein the reference value is areference pressure value, and wherein generating a new reference valuecomprises: for each reference pressure of the selected referencepressures that originated from an area in which pressure changed inexcess of a threshold amount of pressure since that reference pressurewas determined, adjusting that reference pressure by an amount ofpressure change that occurred since that reference pressure wasdetermined; and computing the new reference value using the adjustedreference pressures.
 9. The method of claim 1, further comprising: aftertransmitting the reference value, determining occurrences of thereference value being valid and being not valid; in response to thereference value being valid, transmitting the reference value from thetransmitter to the mobile device or another mobile device; and inresponse to the reference value not being valid: generating a newreference value; and transmitting the new reference value from thetransmitter to the mobile device or the other mobile device.
 10. Themethod of claim 1, further comprising: after transmitting the referencevalue, determining that a first broadcast is not scheduled at a firsttime; in response to the first broadcast being not scheduled at thefirst time, determining occurrences of the reference value being validand being not valid; in response to the reference value being valid,determining if a second broadcast is scheduled at a second time that isafter the first time; and in response to the reference value being notvalid: generating a new reference value; and determining if the secondbroadcast is scheduled at the second time.
 11. The method of claim 1,wherein selecting the reference data further comprises: selecting onlyreference data from each weather station within the cellular element orwithin a threshold distance from part of the cellular element.
 12. Themethod of claim 1, wherein selecting the reference data furthercomprises: selecting only reference data from the nearest n weatherstations to part of the cellular element.
 13. The method of claim 1,wherein the reference data is selected based on an age or a quality inaddition to the proximity condition, and selecting the reference datafurther comprises: selecting only reference data with an age that isbelow a threshold age value, selecting only the n most-recently providedreference data, selecting only reference data with a quality that isabove a threshold quality value, or selecting only the n highest-qualityreference data.
 14. The method of claim 1, wherein if none of thereference data meet the proximity condition, the method comprises:determining a new cellular element; and selecting second reference datathat meet the proximity condition relative to the new cellular element.15. The method of claim 1, wherein the selected reference data includesselected reference pressures, the reference value is a referencepressure value of a reference altitude, and the method furthercomprises: receiving, at the mobile device, the reference pressure valuethat was transmitted by the transmitter; determining occurrences of thereference pressure value being valid and being not valid at a currenttime; in response to the reference pressure value being valid:determining a first representative reference pressure value using thereference pressure value received from the transmitter; and using thefirst representative reference pressure value, the reference altitude,and a pressure value measured by a pressure sensor of the mobile deviceto estimate an altitude of the mobile device; and in response to thereference pressure value being not valid: determining a new referencepressure value by adjusting the reference pressure value received fromthe transmitter based on changes in pressure in the transmitter network;determining a second representative reference pressure value using thenew reference pressure value; and using the second representativereference pressure value, the reference altitude, and the pressure valueto estimate the altitude of the mobile device.
 16. The method of claim15, wherein determining occurrences of the reference pressure valuebeing valid and being not valid comprises: receiving, from thetransmitter, an expiration time of the reference pressure value; anddetermining that the reference pressure value is valid in response tothe current time being before the expiration time, and determining thatthe reference pressure value is not valid in response to the currenttime being after the expiration time; or determining a time at whichpressure in the transmitter network is expected to change by a thresholdamount of pressure since the reference pressure value was determined;determining, based on the determined time, the expiration time for thereference pressure value before which the reference pressure value isvalid and after which the reference pressure value is not valid, whereinthe expiration time is the determined time or a time that precedes thedetermined time by a threshold amount of time; and determining that thereference pressure value is valid in response to the current time beingbefore the expiration time, and determining that the reference pressurevalue is invalid in response to the current time being after theexpiration time.
 17. The method of claim 15, wherein determining a firstrepresentative reference pressure value comprises: selecting, from mreceived reference pressure values, the n most-recently determinedreference pressure values, wherein m is greater than n, and wherein then reference pressure values include the reference pressure valuereceived from the transmitter; and computing the first representativereference pressure value by combining the n selected referencepressures; selecting, from m received reference pressure values, the nreference pressure values having the longest validity times, wherein mis greater than n, and wherein the n reference pressure values includethe reference pressure value received from the transmitter; andcomputing the first representative reference pressure value by combiningthe n selected reference pressures; or selecting, from m receivedreference pressure values, the n reference pressure values from nrespective transmitters that are closet to an estimated location of themobile device, wherein m is greater than n, and wherein the n referencepressure values include the reference pressure value received from thetransmitter; and computing the first representative reference pressurevalue by combining the n selected reference pressures.
 18. The method ofclaim 15, wherein determining a new reference pressure value comprises:adjusting the reference pressure value by an amount of pressure changethat occurred since the reference pressure value was determined, whereinthe new reference pressure value is the result of adjusting thereference pressure value; determining an estimated position of themobile device; determining an expected amount of change in pressurebetween the estimated position of the mobile device and a previousestimated position of the mobile device at which the reference pressurevalue was received; and adjusting the reference pressure value by theexpected amount of change in pressure, wherein the new referencepressure value is the result of adjusting the reference pressure value;or determining an estimated position of the mobile device; determiningan expected amount of change in pressure between the estimated positionof the mobile device and the transmitter; and adjusting the referencepressure value by the expected amount of change in pressure, wherein thenew reference pressure value is the result of adjusting the referencepressure value.
 19. One or more non-transitory machine-readable mediaembodying program instructions that, when executed by one or moremachines, cause the one or more machines to implement the method ofclaim
 1. 20. The method of claim 1, wherein the cellular element is alocation of the transmitter, a coverage area of the transmitter, a cellsector of the transmitter, or a beam of the transmitter.